US12007363B2 - Measuring method and measuring device - Google Patents
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- US12007363B2 US12007363B2 US17/459,627 US202117459627A US12007363B2 US 12007363 B2 US12007363 B2 US 12007363B2 US 202117459627 A US202117459627 A US 202117459627A US 12007363 B2 US12007363 B2 US 12007363B2
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- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
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- G01N29/043—Analysing solids in the interior, e.g. by shear waves
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Definitions
- Embodiments described herein relate generally to a measuring method and a measuring device.
- AE acoustic emission
- elastic waves generated along with the growth of fatigue cracks in a material are detected as a voltage signal (that is, an AE signal) using an AE sensor having a piezoelectric element.
- position evaluation analysis based on an AE method in principle, it is possible to estimate a two-dimensional position associated with a position of an occurrence source in which fatigue cracks have occurred by means of three or more sensors installed on a surface of a structural object.
- a measuring device including an AE sensor needs to be fixed in contact with a structural object which generates elastic waves and an object to be measured, a measurement range, or a measurement environment are limited in some cases.
- FIG. 1 is a side view for explaining a measuring method in a first embodiment.
- FIG. 2 is a graph for describing the results of calculating a phase velocity with respect to a frequency for an A0 mode and an S0 mode of Lamb waves.
- FIG. 3 is a plan view illustrating an example of a constitution of a sensor array of the measuring device in the first embodiment.
- FIG. 4 is a side view of the sensor array at a position C illustrated in FIG. 3 when viewed in a Z direction.
- FIG. 5 is a side view illustrating a part of a constitution of the measuring device in the first embodiment.
- FIG. 6 A is a plan view for explaining a direction and an angle when a structural object is viewed from one sensor included in the sensor array.
- FIG. 6 B is a perspective view for explaining a direction and an angle when a structural object is viewed from one sensor included in the sensor array.
- FIG. 6 C is a perspective view for explaining a direction and an angle when a structural object is viewed from one sensor included in the sensor array.
- FIG. 7 is a graph illustrating an example of a plot showing a change in normalized amplitude with respect to a deviation in azimuth angle.
- FIG. 8 is a plan view for explaining a positional relationship between the sensor array and an occurrence source of elastic waves.
- FIG. 9 is a plan view for explaining a positional relationship between the sensor array and an occurrence source of elastic waves.
- FIG. 10 is a graph for describing the results of calculating a normalized amplitude with respect to a deviation in azimuth angle.
- FIG. 11 is a graph for describing the results of obtaining a correlation relation between a distance between a reference position of the sensor array and an occurrence source and a half value.
- FIG. 12 is a block diagram of the measuring device in the first embodiment.
- FIG. 13 is a block diagram of a signal processing part illustrated in FIG. 12 .
- FIG. 14 is a schematic diagram for explaining a process in a feature amount extraction part illustrated in FIG. 13 .
- FIG. 15 is a flowchart of a process performed by means of the feature amount extraction part illustrated in FIG. 13 .
- FIG. 16 is a flowchart of a process performed by means of a position estimation part illustrated in FIG. 13 .
- FIG. 17 is a side view for explaining a positioning method in the related art associated with an occurrence source of elastic waves in a structural object.
- FIG. 18 is a plan view illustrating a modified example of the constitution of the sensor array of the measuring device in the first embodiment.
- FIG. 19 is a side view of the sensor array when viewed from a Z direction at position C illustrated in FIG. 18 .
- elastic waves such as Lamb waves and Rayleigh waves propagating at a velocity v ae in the structural object 11 formed of a solid material are radiated from a surface 11 a of the structural object 11 into the air as sound waves (elastic waves) 101 .
- the sound waves 101 diffuse into the air at a velocity v air .
- Lamb waves (elastic waves) mainly vibrate particles of the solid material of the surface 11 a and a point sound source 102 is generated in the surface 11 a .
- the sound waves 101 are radiated from the point sound source 102 into the air.
- the point sound source 102 moves in a propagation direction parallel to the surface 11 a at a velocity v ae specific to the solid material.
- the sound waves 101 produced by the moved point sound source 102 form a wavefront 103 having the same phase on a line inclined to have a prescribed angle T from the surface 11 a toward the air side.
- the angle ⁇ is expressed by the following Expression (1).
- X direction two directions parallel to the surface 11 a of the structural object 11 and orthogonal to each other are referred to as an “X direction” and a “Y direction” and a direction parallel to a thickness direction of the structural object 11 and orthogonal to the X direction and the Y direction is referred to as a “Z direction.”
- Z direction two directions parallel to the surface 11 a of the structural object 11 and orthogonal to each other.
- the structural object 11 is a plate made of aluminum and a thickness of the structural object 11 is 3 [mm].
- the elastic waves propagating in the solid material include two types such as p waves which are longitudinal waves and s waves which are transverse waves.
- the structural object 11 is a thin plate such as a plate having a thickness of 3 [mm]
- reflected p waves and reflected s waves are excited due to the reflection at an end surface of the plate and guided waves called Lamb waves (elastic waves) are formed as a whole.
- a propagation state of Lamb waves can be obtained by introducing boundary conditions in the wave expression.
- a propagation velocity of Lamb waves changes in accordance with a frequency. That is to say, Lamb waves have velocity dispersion characteristics.
- a propagation mode of Lamb waves in a plate made of aluminum which is a thin plate includes a symmetric mode (a symmetry (S) mode) and an asymmetric mode (an anti-symmetry (A) mode). The higher the order of each propagation mode, the higher the frequency.
- S symmetry
- A anti-symmetry
- S0 mode S0 mode
- A0 mode A0 mode
- the sound waves 101 are generated in the air adjacent to the surface 11 a of the structural object 11 , that is, a medium around the structural object 11 .
- the angle ⁇ formed by the wavefront 103 of the sound waves 101 and the surface 11 a of the structural object 11 is determined by means of a ratio of the propagation velocity of the elastic waves in the solid material (may be referred to simply as a “velocity” in the specification in some cases) to the propagation velocity of the elastic waves in the air.
- the sound waves 101 radiated from the surface 11 a of the structural object 11 into the air are detected and a position of an occurrence source of the elastic waves in the structural object 11 is estimated.
- the position of the occurrence source is not specifically identified in the Z direction and means a position in an XY plane including the X direction and the Y direction.
- the measuring device 201 includes a sensor array (sensor part) 51 illustrated in FIGS. 3 and 4 and a position estimation device (a position estimation mechanism) 60 which will be described later.
- the sensor array 51 includes a plurality of ultrasonic sensors (sensors) 10 - 1 , 10 - 2 , . . .
- these ultrasonic sensors will be referred to as an “ultrasonic sensor 10 .”
- the ultrasonic sensor 10 detects the sound waves 101 in a non-contact manner.
- the sound waves 101 are generated when elastic waves generated in the structural object 11 formed of a solid material are radiated into the air.
- the solid material is, for example, a composite material such as carbon fiber reinforced plastic in addition to concrete, iron, aluminum, ceramics, and the like, but is not limited to a specific solid material.
- the plurality of ultrasonic sensors 10 are disposed in the air at a prescribed height h a in the Z direction from the surface 11 a of the structural object 11 , and as illustrated in FIG. 4 , are provided not to come into contact with the structural object 11 . As illustrated in FIG.
- the plurality of ultrasonic sensors 10 are disposed on a circle 14 having a reference position 16 as a center and a distance r a as a radius at substantially equal intervals in a circumferential direction when viewed in a plan view. That is to say, the plurality of ultrasonic sensors 10 are disposed about the reference position 16 in an annular shape.
- the reference position 16 is a position on the surface 11 a of the structural object 11 in the air moving at the height h a in the Z direction from a reference position (a prescribed reference position) 110 .
- the plurality of ultrasonic sensors 10 are disposed at an angle (a prescribed inclination angle) Ta with respect to a normal 112 of the surface 11 a passing through the reference position 110 .
- the ultrasonic sensor 10 is a detection device having directivity for elastic waves in a detection direction.
- Axes 12 - m indicating a maximum sensitivity of the directivity of an ultrasonic sensor 10 - m intersect each other at the reference position 110 and focus at one point at the reference position 110 .
- m represents a natural number from 1 to j.
- An angle ⁇ a formed by the axes 12 - m of the ultrasonic sensor 10 - m and the normal 112 is expressed by the following Expression (3) on the basis of the velocity v ae of the elastic waves in the solid material of the structural object 11 to be measured and the velocity v air of the sound waves 101 in the air.
- ⁇ a arcsin ⁇ ( v air v ae ) ( 3 )
- the plurality of ultrasonic sensors 10 are disposed at a certain distance (a prescribed distance) r a from the reference position 110 when viewed in a plan view. That is to say, a separation distance between a detection port 13 - m of the ultrasonic sensor 10 - m and the reference position 16 in the XY plane is the distance r a .
- the sensor array 51 includes a frame member 40 configured to support the plurality of ultrasonic sensors 10 in an annular shape when viewed in a plan view as described above and in a discrete manner, in addition to the plurality of ultrasonic sensors 10 .
- the frame member 40 is omitted.
- the frame member 40 is formed to have the reference position 16 as a center in an annular shape.
- the eight ultrasonic sensors 10 - 1 , . . . , and 10 - 8 are installed on an inner circumferential side of the frame member 40 by means of connecting members or the like (not shown).
- the ultrasonic sensors 10 - m are disposed so that the axes 12 - m gather and intersect at the reference position 110 below the sensor array 51 .
- the detection port 13 - m of the ultrasonic sensor 10 - m is disposed to hang below the frame member 40 and faces the reference position 110 when viewed in a plan view.
- the sensor array 51 may include a member suitable for installing the plurality of ultrasonic sensors 10 as described above, in addition to the frame member 40 .
- FIG. 5 illustrates only the ultrasonic sensor 10 - 1
- the connecting members (not shown) between the ultrasonic sensor 10 and the frame member 40 may be configured so that a position of the ultrasonic sensor 10 - m in the Z direction and an angle Ta formed by the axes 12 - m with respect to the normal 112 can be changed.
- the frame member 40 may be movably installed or fixed in a space in the surface 11 a of the structural object 11 to be measured on the air side and may be configured to be able to fly by being connected to an air vehicle or the like.
- the detection port 13 - m configured to detect ultrasonic waves in the ultrasonic sensor 10 - m is directed to the reference position 110 .
- the directivity of the ultrasonic sensor 10 is regarded as a problem of a sound field formed in a range on a disk having a prescribed radius embedded in an infinite rigid wall and vibrating at a prescribed angular frequency. Assuming that a sound field is formed in a long-distance field, when an azimuth angle of the axes 12 - m of the ultrasonic sensor 10 - m illustrated in FIGS.
- a directivity function which is a function of an angle ⁇ indicating a directivity in the XY plane is expressed by the left side expressed by the following Expression (4) and is approximated so that the directivity function has the right side expressed by Expression (4) using the angle ⁇ 0 formed by a reference axis 32 and the axes 12 - m and a wave number k of elastic waves.
- J 1 in Expression (4) is a first-order Bessel function.
- an angle ⁇ deviated in a detection direction in which the directivity of the ultrasonic sensor 10 is the highest and in an arrival direction of the reference positions 16 and 110 of the elastic waves is expressed as the following Expression (5) and the foregoing Expression (1) through geometric calculation using the velocity v ae of the elastic waves in the structural object 11 .
- ⁇ arccos ⁇ 1 ⁇ (sin ⁇ ) 2 (1 ⁇ cos ⁇ azm ) ⁇ (5)
- FIG. 7 shows the result of calculating numerical values of amplitude characteristics of the sound waves 101 with an angle representing an amount of deviation in an azimuth angle (an azimuth angle illustrated in FIG. 7 ). As illustrated in FIG.
- a change in intensity of an AE signal (a signal) to be detected is shown on the basis of an angle difference between a direction in which the sound waves 101 arrive (a direction in which an axis is directed) and a direction in which the elastic waves arrive from an occurrence source toward the reference position 16 (a detection direction of the elastic waves).
- a distance L between the reference position 16 and the occurrence source 120 of the elastic waves is, for example, several times a size of the sensor array 51 , that is, a diameter thereof, when viewed in a plan view and is regarded to be finite
- the elastic waves arriving from the occurrence source 120 at the sensor array 51 are incident on the plurality of ultrasonic sensors 10 disposed in an annular shape about the reference position 16 when viewed in a plan view at different azimuth angles ⁇ azm .
- the elastic waves arriving from the occurrence source 120 at the sensor array 51 are incident on the plurality of ultrasonic sensors 10 at substantially the same azimuth angle ⁇ . That is to say, the angle ⁇ src indicates a detection in which the elastic waves (hereinafter may be referred to as “AE waves” in some cases) arrive at the sensor array 51 , that is, a detection direction of the AE waves.
- AE waves the elastic waves
- the angle ⁇ src represents an angle formed by a direction in which an AE signal (or AE waves) is detected with respect to an axis 22 using the axis 22 parallel to the X direction and passing through the reference position 16 when viewed in a plan view as a reference line.
- the azimuth angle ⁇ azm at which the elastic waves are incident on the ultrasonic sensor is represented by the following Expressions (6) and (7).
- the angle ⁇ src indicates a direction from a detection position of the elastic waves when viewed in a plan view, that is, the reference position 16 toward the occurrence source.
- the angle ⁇ a is determined using a relative disposition of the ultrasonic sensors 10 and represents an angle formed by the axis 12 - m of each of the ultrasonic sensors 10 - m and the axis 22 when viewed in a plan view.
- ⁇ azm ⁇ ⁇ src - arctan ⁇ ⁇ r ⁇ sin ⁇ ⁇ ⁇ ⁇ src L + r ⁇ cos ⁇ ⁇ ⁇ ⁇ src ⁇ ( 6 )
- FIG. 10 is a graph obtained by numerically calculating a change in normalized amplitude value (information concerning an intensity) with respect to the azimuth angle ⁇ azm as information regarding an intensity of the AE signal on the basis of Expressions (5) and (6) using the same parameters as in the above example and plotting the calculation results. If the distance L is increased to 0.1 [m], 0.2 [m], and 1.0 [m], an azimuth angle ⁇ azm of a peak does not change substantially and a half-value angle decreases. An angle ⁇ azm of the peak indicates a direction in which there is the occurrence source 120 when viewed from the reference position 16 of the sensor array 51 . A half-value angle of a plot of the normalized amplitude value with respect to the angle ⁇ azm depends on the distance L and increases when the distance r a decreases.
- FIG. 11 shows a relationship between the distance L and the half-value angle when the following values are substituted into Expressions (5) to (7) on the assumption that the distance r a is 95 [mm], a frequency of the elastic waves is 200 [kHz], a velocity of the elastic waves is 1530 [m/s], a sound velocity in the air is 340.29 [m/s], and a radius of a vibrator is 3.5 [mm].
- a half-value width when the distance L is changed is calculated in advance and a calibration curve between the distance L and the half-value width is created.
- an amplitude value for each of the discrete azimuth angles ⁇ azm is obtained.
- the obtained amplitude value is fitted by means of Expressions (6) and (7), a peak angle and a half-value angle are calculated, a direction inclined with respect to the axis 22 is obtained using the peak angle as the angle ⁇ src , and the distance L is obtained by making the half-value width fit to the above-described calibration curve. It is possible to estimate a position in which there is the occurrence source 120 when viewed from the sensor array 51 using this calculated information.
- A represents a scaling factor associated with an amplitude and ⁇ represents a distribution concentration parameter associated with a distance.
- the fitting function is not particularly limited as long as the fitting function has an element which leads to a relationship between the distance L and the half-value angle.
- the plurality of ultrasonic sensors 10 are disposed at equal intervals in the circumferential direction on a virtual circle 14 having a radius centered on the reference position 16 and having a distance r a .
- the measuring device 201 in the first embodiment includes the sensor array 51 and the position estimation device 60 .
- the position estimation device 60 includes amplifiers 62 - 1 to 62 - j having the same total number j as the plurality of ultrasonic sensors 10 , bandpass filters (BPS) 64 - 1 to 64 - j , a signal processing part 70 , and an output part 90 .
- the amplifiers 62 - 1 to 62 - j amplify a voltage signal (information regarding an intensity of a signal of the elastic waves) associated with the sound waves 101 output from the ultrasonic sensors 10 - 1 to 10 - j with, for example, a prescribed gain such as a voltage gain.
- the BPFs 64 - 1 to 64 - j remove noise components outside of a prescribed band of the voltage signals amplified by the amplifiers 62 - 1 to 62 - j and output a voltage signal within a prescribed band.
- Types of BPFs 64 - 1 to 64 - j are not particularly limited as long as the BPFs 64 - 1 to 64 - j are filters capable of performing the above-described operations.
- the signal processing part 70 detects an amplitude associated with the sound waves 101 detected by the plurality of ultrasonic sensors 10 and estimates a position of the occurrence source 120 through a prescribed arithmetic process.
- the output part 90 includes a display device or the like which outputs the estimated position of the occurrence source 120 to the outside, and for example, displays the estimated position of the occurrence source 120 directly or remotely.
- the signal processing part 70 includes a feature amount extraction part 72 , a position estimation part 74 , and a sensor disposition storage part 76 .
- the feature amount extraction part 72 extracts information regarding an amplitude of the sound waves 101 at least as information regarding an amplitude of the elastic waves.
- FIG. 14 shows a typical example of a time change of a voltage signal associated with the amplitude of the sound waves 101 . As illustrated in FIG. 14 , the amplitude of the voltage signal increases immediately after the start of detection and is larger in an initial time zone t1 than in the subsequent time. The amplitude of the voltage signal after a maximum peak decreases with the passage of time and remains weak.
- the feature amount extraction part 72 Based on such characteristics of the time change in the amplitude of the voltage signal, the feature amount extraction part 72 performs the processing of the flowchart shown in FIG. 15 . If the measurement is started, the feature amount extraction part 72 determines whether the voltage signal exceeds a prescribed amplitude threshold value V TH (Step S 501 ). When it is determined that the voltage signal exceeds the prescribed threshold value, a maximum value of the amplitude is maintained in the subsequent time. The above-described maximum value of the amplitude is maintained until the amplitude continues to fall below the prescribed threshold value for a certain time t 2 (Step S 502 ).
- Step S 503 When it is determined that the amplitude falls below the threshold value V TH for a certain time t 2 , it is determined that a series of elastic waves has converged (Step S 503 ), the maximum value of the amplitude at that time is extracted (Step S 504 ) and the extracted maximum value is transmitted to the position estimation part 74 .
- Step S 512 data concerning the plurality of discrete angles ⁇ azm and amplitude values at the angles ⁇ azm is created on the basis of the information regarding the azimuth angle ⁇ azm of the ultrasonic sensor 10 (Step S 512 ). Fitting is performed on the created discrete data through a prescribed continuous function (Step S 513 ) and a peak angle and a half-value angle are obtained (Step S 514 ).
- the peak angle corresponds to a direction in which there is the occurrence source 120 when viewed from the sensor array 51 and the half-value angle corresponds to the distance L.
- a relationship between the half-value angle and the distance L may be calculated each time on the basis of the foregoing Expressions (5) and (6) or a data table may be created in advance.
- two-dimensional plane coordinates of the occurrence source 120 may be calculated on the basis of the direction in which there is the occurrence source 120 when viewed from the sensor array 51 , that is, the detection direction of the elastic waves and the distance L.
- the feature amount extraction part 72 , the position estimation part 74 , the sensor disposition storage part 76 , and the output part 90 may be functional parts which function using software or may be functional parts which function using hardware such as an LSI or FPGA.
- the measuring method in the first embodiment includes estimating a position of the occurrence source 120 of the elastic waves in the structural object 11 formed of a solid material by detecting the sound waves 101 using the sensor array 51 having the plurality of ultrasonic sensors 10 .
- the measuring method in the first embodiment includes detecting the sound waves 101 generated when the elastic waves generated in the structural object 11 are radiated from the surface 11 a into the air from the structural object 11 to be measured in a non-contact manner and estimating a position of the occurrence source 120 of the elastic waves on the basis of the information regarding the intensity of the signal of the detected sound waves 101 .
- elastic waves such as Lamb waves generated in the structural object 11 are detected by the ultrasonic sensor 10 having directivity as ultrasonic waves such as the sound waves 101 radiated from the surface 11 a into the air.
- the ultrasonic sensor 10 having directivity as ultrasonic waves such as the sound waves 101 radiated from the surface 11 a into the air.
- the ultrasonic sensor 10 In order to detect the sound waves 101 using only the ultrasonic sensor 10 which is not in contact with the structural object 11 , it is not necessary to dispose the measuring device including an AE sensor to be in contact with the structural object 11 as in the position evaluation analysis based on the AE method in the related art. For this reason, the present invention can be applied to the estimation of an occurrence source of the elastic waves in a structural object in which it is difficult to install an AE sensor on the surface of the structural object.
- the present invention can be performed even in an environment in which it is difficult to install an AE sensor on a structure object. As a result, it is possible to increase degrees of freedom of the structural object 11 to be measured and freedom in a measurement range or a measurement environment associated with the position of the occurrence source.
- two AE sensors 311 and 312 are disposed on a surface 100 a of a structural object 100 at intervals from each other.
- the AE sensors 311 and 312 it is possible to determine a position of the occurrence source 120 on the basis of information concerning a difference between arrival times t1 and t2 at which the elastic waves arrive at the AE sensors 311 and 312 .
- the accuracy of the position of the occurrence source 120 estimated as in the related art does not decrease depending on the accuracy of determining an arrival time and it is not necessary to dispose a large number of sensors in a wide range in advance to estimate a position in a wide range.
- the measuring method in the first embodiment includes estimating, when the position of the occurrence source 120 is estimated, at least one of the direction from the reference position 16 (the detection position of the elastic waves) of the sensor array 51 toward the occurrence source 120 and the distance from the reference position 16 to the occurrence source 120 on the basis of the information regarding the detection direction of the elastic waves and the information regarding the intensity of the elastic waves is estimated. According to the measuring method in the first embodiment, it is possible to estimate the position of the occurrence source 120 on the basis of the correspondence relationship between the arrival direction of the elastic waves and the intensity using the plurality of ultrasonic sensors 10 .
- the measuring method in the first embodiment includes detecting, when the position of the occurrence source 120 is estimated, the plurality of azimuth angles ⁇ azm used for detecting the sound waves 101 , that is, the detection angles in a discrete manner and obtaining information of an actual measurement function (not shown) which represents the change in the amplitude of the sound waves with respect to the detection angles by fitting the continuous function to the plot of the amplitude as information concerning the intensity of the sound waves 101 at the detection angles for the plurality of detection angles. Based on the information of the actual measurement function, at least one of the direction from the reference position 16 of the elastic waves toward the occurrence source 120 and the distance L from the reference position 16 to the occurrence source 120 is estimated.
- the measuring method in the first embodiment specifically, since the relationship between the angle ⁇ azm and the amplitude of the sound waves 101 is fitted through a theoretical continuous function, it is possible to obtain information regarding the relationship between the angle ⁇ azm and the amplitude of the sound waves 101 which is not included in the discrete data.
- the measuring method in the first embodiment includes detecting elastic waves in a non-contact manner using the plurality of ultrasonic sensors 10 as AE sensors and using a directivity function based on a resonance frequency and a vibrator radius of the ultrasonic sensor 10 as a continuous function. According to the measuring method in the first embodiment, it is possible to estimate a position of the occurrence source 120 when viewed in a plan view using the continuous function optimal for the ultrasonic sensor 10 by introducing parameters associated with the ultrasonic sensor 10 .
- the von Mises distribution function may be used as a continuous function. When the von Mises distribution function is used, a calculation process of calculating an actual measurement function by mainly fitting the continuous function to discrete data is simplified and an amount of calculation can be reduced.
- the measuring device 201 in the first embodiment includes the sensor array 51 and the position estimation device 60 .
- the sensor array 51 has the plurality of ultrasonic sensors 10 configured to detect the sound waves 101 generated in the structural object 11 formed of a solid material in a non-contact manner.
- the position estimation device 60 estimates a position of the occurrence source 120 on the basis of the information regarding an intensity of a signal of the sound waves 101 detected by the ultrasonic sensor 10 .
- the elastic waves generated in the structural object 11 are detected by the ultrasonic sensor 10 having directivity as ultrasonic waves such as the sound waves 101 .
- the sound waves 101 is detected using only the ultrasonic sensor 10 which is not in contact with the structural object 11 , it may not be necessary to dispose the measuring device including the AE sensor to be in contact with the structural object 11 as in the position evaluation analysis based on the AE method in the related art. For this reason, it can also be applied to the estimation of the occurrence source of elastic waves in a structural object in which it is difficult to install an AE sensor on a surface of the structural object. As a result, it is possible to increase degrees of freedom of the structural object 11 to be measured and freedom in a measurement range or a measurement environment associated with the position of the occurrence source.
- the position estimation device 60 includes a detection direction acquisition part 81 , an intensity acquisition part 82 , and a position estimation part (an estimation part) 74 .
- the detection direction acquisition part 81 acquires information regarding a detection direction of sound waves 101 in each ultrasonic sensor 10 included in the plurality of ultrasonic sensors 10 .
- the intensity acquisition part acquires information regarding an intensity of a signal of the sound waves 101 detected by each ultrasonic sensor 10 .
- the position estimation part 74 described above includes the detection direction acquisition part 81 and the intensity acquisition part 82 . That is to say, in the position estimation part 74 , as described with reference to Step S 512 of the flowchart shown in FIG.
- a maximum peak angle ⁇ azm represents an angle ⁇ src indicating a detection direction of the sound waves 101 in each ultrasonic sensor 10 .
- the amplitude value at the angle ⁇ azm is associated with the intensity of the signal of the sound waves 101 detected by each ultrasonic sensor 10 .
- the position estimation part 74 estimates an angle ⁇ src and a distance L from the reference position 16 to the occurrence source 120 as a direction from the reference position 16 of the sensor array 51 toward the occurrence source 120 on the basis of the information regarding the detection direction of the sound waves 101 and the information regarding the intensity of the signal of the sound waves 101 detected by each ultrasonic sensor 10 .
- the measuring device 201 in the first embodiment it is possible to acquire the information regarding the direction of the occurrence source 120 when viewed from the sensor array 51 and the distance L between the sensor array 51 and the occurrence source 120 on the basis a correspondence relationship between the arrival direction of the sound waves 101 detected by each ultrasonic sensor 10 and the intensity and estimate the position of the occurrence source 120 .
- the position estimation device 60 includes a detection angle acquisition part 85 , a function acquisition part 83 , and the position estimation part 74 .
- the detection angle acquisition part 85 acquires information regarding a plurality of detection angles of the sound waves 101 obtained in a discrete manner by each ultrasonic sensor 10 included the sensor array 51 .
- the function acquisition part 83 acquires information of an actual measurement function representing a change in amplitude with respect to an angle (a detection angle) ⁇ azm by fitting a continuous function to the plot of the amplitude (the information regarding the intensity) of the sound waves 101 with respect to the detection angle of the plurality of ultrasonic sensors 10 of the sensor array 51 .
- the position estimation part 74 described above includes the detection angle acquisition part 85 and the function acquisition part 83 . That is to say, in the detection angle acquisition part 85 of the position estimation part 74 , as described with reference to Steps S 513 and S 514 of the flowchart shown in FIG. 16 , discrete data is created on the basis of the amplitude values at the angle ⁇ azm and the angle ⁇ azm detected by the plurality of ultrasonic sensors 10 .
- the function acquisition part 83 of the position estimation part 74 fits the created discrete data with a prescribed continuous function and uses a function which fits best as an actual measurement function.
- the position estimation part 74 estimates an angle ⁇ src indicating the direction from the reference position 16 of the sensor array 51 toward the occurrence source 120 and a distance L from the reference position 16 to the occurrence source 120 on the basis of the information regarding the actual measurement function acquired by the function acquisition part 83 .
- the AE sensor capable of detecting ultrasonic waves is used as a sensor configured to detect sound waves 101 in a state of non-contact with the structural object 11 .
- the continuous function described above is a directivity function expressed by Expression (3) on the basis of the resonance frequency and the vibrator radius of the ultrasonic sensor (that is, the AE sensor) 10 .
- the measuring device 201 in the first embodiment it is possible to estimate a position of the occurrence source 120 when viewed in the plan view using a continuous function optimal for the ultrasonic sensor 10 .
- the von Mises distribution function may be used as the continuous function. In that case, the calculation process of fitting the continuous function to the discrete data to calculate the actual measurement function can be simplified and the amount of calculation can be reduced.
- the plurality of ultrasonic sensors 10 are disposed in an annular shape about the reference position 16 when viewed in a plan view, that is, when viewed from the Z direction. According to the measuring device 201 in the first embodiment, since the distance r a between the plurality of ultrasonic sensors 10 and the reference position 16 is constant, the angle ⁇ src can be easily calculated using Expression (5) on the basis of the discrete data.
- the axes 12 - m indicating the maximum sensitivity of the directivity of each of the plurality of ultrasonic sensors 10 - m intersect each other at the reference position 110 of the surface 11 a of the structural object 11 and are focused at one point at the reference position 110 .
- the angle Ta formed by the axes 12 - m and the normal 112 is constant and the reference positions 110 and 16 are clearly set, the angle ⁇ src can be easily calculated using Expression (4) on the basis of the discrete data.
- a measuring method and a measuring device in a modified example of the first embodiment will be described below.
- constituent elements of the modified example that are the same as the measuring method and the measuring device 201 in the first embodiment will be denoted by reference numerals that are the same as the first embodiment and duplicate description of the modified example and the first embodiment will be omitted.
- both of the direction in which there is the occurrence source 120 (the direction from the detection position toward the occurrence source) when viewed from the reference position 16 in the sensor array and the distance L from the reference position 16 to the occurrence source 120 (the distance from the detection position to the occurrence source) can be estimated.
- the position of the occurrence source 120 can be specifically identified using the information regarding either the direction in which there is the occurrence source 120 when viewed from the reference position 16 , that is, the angle ⁇ src and the distance L, only one of the angle ⁇ src and the distance L may be estimated.
- a sensor array 52 shown in FIGS. 18 and 19 can be exemplified.
- the plurality of ultrasonic sensors 10 may be disposed concentrically when viewed in a plan view with the reference position 16 as a center.
- the sensor array 52 may include ultrasonic sensors 10 - 11 to 10 -( 10 +q) having a total number of p separated by a distance r b different from a distance r a with the reference position 16 as a center and disposed in an annular shape, in addition to the ultrasonic sensors 10 - 1 to 10 - j separated by the distance r a with the reference position 16 as a center and disposed in an annular shape.
- the ultrasonic sensors 10 -( 10 +q) mean a ( 10 +q)th ultrasonic sensor 10 corresponding to that of FIGS. 18 and 19 .
- q is a natural number from 1 to p.
- the total numbers j and p are not limited to 8, may be any total number of 2 or more, and may not be equal to each other.
- Axes 12 -( 10 +q) indicating the maximum sensitivity of the directivity of the ultrasonic sensor 10 -( 10 +q) intersect each other at the reference position 110 and form an angle ⁇ b with respect to the normal 112 when viewed in a side view.
- ⁇ b arcsin ⁇ ( v air v ae ⁇ ⁇ 2 ) ( 11 )
- the ultrasonic sensor 10 - m and the ultrasonic sensor 10 -( 10 +p) are disposed at the same height in the Z direction.
- the ultrasonic sensors 10 - m and 10 -( 10 +p) are disposed at the same height as described above, the efficiency of an installation space can be improved.
- the ultrasonic sensor 10 - q (some sensors included in the plurality of sensors) is disposed at an angle (an inclination angle) ⁇ b different from that of the ultrasonic sensor 10 - m (the remaining sensors) with respect to the normal 112 passing through the reference position 110 on the surface 11 a of the structural object 11 . If the angle ⁇ b is set in accordance with the propagation velocity v ae in the structural object 11 as in Expression (11), the sensor array 52 can detect two types of elastic waves having different propagation velocities in the structural object 11 .
- a plurality of ultrasonic sensors 10 are disposed in three or more concentric circle shapes with the reference position 16 as a center and an angle formed by the axis indicating the maximum sensitivity of the directivity of each ultrasonic sensor 10 and the normal 112 is set in consideration of the velocity of the elastic waves in the structural object 11 , it is possible to detect three or more types of elastic waves having different propagation velocities in the structural object 11 . Therefore, the number of concentric circles in which the plurality of ultrasonic sensors 10 are disposed about the reference position 16 may not have to be limited to a specific number.
- a modified example of a constitution of a sensor array different from the sensor arrays 51 and 52 may be conceivable. If the angle formed by the axis indicating the maximum sensitivity of the directivity of each ultrasonic sensor 10 and the normal 112 is determined and the distance between the detection port of the elastic waves in each ultrasonic sensor 10 and the reference position 16 is determined, the height from the surface 11 a and the distances from the reference position 16 of the plurality of ultrasonic sensors 10 may be different from each other.
- the plurality of ultrasonic sensors 10 may be disposed to draw a rectangular shape, an elliptical shape, a diamond shape, or any other shape when viewed in a plan view.
- the plurality of ultrasonic sensors 10 may be disposed in a spiral shape when viewed in a side view.
- the sensor array 51 having the plurality of ultrasonic sensors 10 detects the sound waves 101 generated in the structural object 11 in a non-contact manner.
- the distance L is regarded to be infinite as described above, only one ultrasonic sensor 10 can detect the sound waves 101 in a non-contact manner.
- the distance L is regarded to be finite, substantially two or more ultrasonic sensors 10 are required.
- the elastic waves generated in the structural object 11 formed of a solid material are detected using the sound waves 101 in a non-contact manner and the position of the occurrence source 120 of the elastic waves is estimated on the basis of the information regarding the intensity of the signal of the detected elastic waves, it is possible to increase a degrees of freedom of the object to be measured, the measurement range, or the measurement environment in which there is the occurrence source 120 of the elastic waves.
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Abstract
Description
θ=arccos{1−(sin ψ)2(1−cos θazm)} (5)
{circumflex over (θ)}src=θa+θsrc (7)
f(θ)=A·e κ COS(θ−θ
P m:(r a ,nθ a)(m=1, . . . ,j) (9)
θa=2π/j (10)
P q:(r b ,nθ b)(q=1, . . . ,p) (12)
θb=2π/p (13)
Claims (14)
θ=arccos{1−(sin ψ)2(1−cos θazm)} (2),
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